Gravity displacement sterilizer



Nov. 3, 1970 c. E. GALLAGHER ET 3,537,312

GRAVITY DISPLACEMENT STERILIZER Filed Dec. 13. 1967 2 Sheets-Sheet 1INVENTOR. (M46155 .5. GRLLAGHAEK Dan/0A0 A. lm' L/AMES H. i l 6 M M KiMMNov. 3, 1970 c. E. GALLAGHER HAL GRAVITY DISPLACEMENT STERILIZER 2-S'neets-Sheet 2 Filed Dec. 13. 1967 United States Patent 3,537,812GRAVITY DISPLACEMENT STERILIZER Charles E. Gallagher, Donald A. Gunther,and James H.

Patric, Erie, Pa., assignors to American Sterilizer Company, Erie, Pa.,a corporation of Pennsylvania Filed Dec. 13, 1967, Ser. No. 690,304 Int.Cl. A611 3/00 US. Cl. 21--91 9 Claims ABSTRACT OF THE DISCLOSURE Agravity displacement sterilizer comprising hood, diffuser andintermediate sections and including a gas outlet in the hood section anda gas inlet in the diffuser section. The hood and diffuser sections arein the form of truncated cones with the widest portion thereof connectedto said intermediate section. Diffusion means is located in saiddiffuser section to direct incoming sterilizing gas so it is distributedgenerally uniformly over the entire cross-sectional area of saidintermediate section, said gas distribution being accomplished generallywithout turbulence to provide for a minimum of mixing of the sterilizinggas and air piesent in the sterilizer.

The sterilizer disclosed has a chamber having a configuration such thatgas will pass from the inlet through the sterilizing section of thechamber to the outlet with minimum turbulence and therefore with minimummixing of one with the other. Thus, the gas contents can be moved fromthe inlet to the outlet as a single body and one gas can be readilydisplaced from the chamber by another without the need of expensivevacuum pumps. The diffusing section which starts with the gas input linegradually increases in cross sectional area to the size of thesterilizer section. The purpose of the diffusing section is to reducethe vertical component of velocity of the gas so as to result in minimumturbulence inside the sterilizing chamber, thereby insuring a reasonablynonturbulent exchange of air and gas. The idea is to keep the interfacebetween the gas and :air reasonably stable. At the top of thesterilizing section is a discharge chamber which may be a facsimile ofthe bottom, but inverted. To further minimize turbulence a filter isprovided. This filter can be a sintered ceramic or metal filter, a sackof porous nylon, several layers of perforated sheet material, or a layerof beads.

A preconditioning chamber is connected in series with the inlet whereinthe gas from a source is conditioned by heating, cooling, or mixing.sterilizing gas is normally stored in liquid form. When liquified gas isreleased from its pressure vessel, it immediately starts to boil andvaporize. The preconditioning chamber may be made to promote thetransition from liquid to gas and insure that suitable vaporized gas isintroduced to the diffuser chamber.

Various efforts have been made in the art to admit steam or gas to asterilizing chamber to give optimum, uniform distribution of thesterilizing medium. Examples of patents that show such efforts are Pat.No. 1,850,923, Pat. No. 2,208,552 and Pat. No. 3,150,935, and BritishPatent 1,077,246.

None of these patents have attempted to utilize the admission of thesterilizing medium to displace the air in the sterilizer as a singlebody.

It is known in the sterilizing art that air in the sterilizer during asterilizing cycle and air entrained in the goods to be sterilized is anenemy to all sterilizing processes.

In the sterilizer and process disclosed herein, a casing is providedwith a diffusing chamber at the bottom and a hood at the top. The hoodand diffusing chamber are both made of gradually increasing crosssectional area Patented Nov. 3, 1970 toward the central chamber so thatair or gas can flow from the inlet, through the diffusing chamber to thesterilizing part and thus out through the hood and through the dischargewith a minimum amount of turbulence introduced into the medium. By sodoing and by admitting the gas through the diffusing chamber at a verylow velocity, the air in the chamber can be lifted as a body from thechamber and through the hood to the discharge, thereby removingsubstantially all of the air from the chamber and thereby eliminating anevacuating pump and the inherent expense of maintaining and operatingsuch a pump. Further, when the displacement method is used in accordancewith the process disclosed herein, the walls of the chamber may be mademuch lighter than would be necessary to withstand a vacuum created by avacuum pump were it used to evacuate the chamber and where a positivepressure is not used.

In one embodiment of the invention, beads can be used to fill thediffusing chamber in order to more completely diffuse the gas at thediffuser. These beads provide paths for the air between them and therebydiffuse the gas uniformly over the bottom of the chamber. By providingbeads of the proper size and shape and by providing the correct angle onthe diffusing chamber walls and the hood walls and the correct velocityof gas to prevent turbulence of the sterilizing gas, the air can besubstantially completely removed from the chamber with a minimum wasteof time and gas.

It is, accordingly, an object of the invention to provide an improvedsterilizing apparatus.

Another object of the invention is to provide an improved sterilizingapparatus wherein the sterilizer chamber has a generally streamlinedshape and the sterilizing gas is admitted to the chamber through adiffusing medium whereby the low velocity gas sweeps the entire body ofair in the sterilizer out as a body.

A further object of the invention is to provide an improved sterilizingapparatus wherein a diffusing chamber is provided filled with beadswhich diffuse the sterilizing gas and distribute it evenly throughoutthe chamber.

With the above and other objects in view, the present invention consistsof the combination and arrangement of parts hereinafter more fullydescribed, illustrated in the accompanying drawings, and moreparticularly pointed out in the appended claims, it being understoodthat changes may be made in the form, size, proportions, and minordetails of construction without departing from the spirit or sacrificingany of the advantages of the invention.

In the drawings:

FIG. 1 is an isometric view of the sterilizer according to theinvention;

FIG. 2 is a longitudinal cross-sectional view of the sterilizingchamber; and

FIGS. 3 and 4 are views similar to FIGS. 1 and 2 of other embodiments ofthe invention.

Now with more particular reference to the drawings, and to the methodwhich may be carried out by the drawing, the sterilizing chamber isgenerally indicated at 10 having side 14. It has an intermediate orsterilizing chamber 11 which may be considered to be the sterilizingsection, a hood 12 integrally attached to the sterilizing chamber and adiffusing section 13 likewise attached to the sterilizing chambersection. The sterilizer is provided with an inlet 15 for air, gas, andsteam and an outlet 20 for air, gas, and steam to be exhausted.

The hood 12 and the diffusing section 13 each provide means to directthe main body of air from the sterilizing chamber 11 to the outlet witha minimum amount of turbulence so that gas entering the diffusingchamber through the inlet 15 will have its velocity progressivelydecreased as it moves through the beads 17 and when it reaches thetransition from the diffusing section to the sterilizing section, thevelocity of gas will be the same as the velocity of the gas at theentrance to the hood 12, since the passageway through this portion willbe substantially constant in cross sectional area.

The chamber itself, including the exhaust hood and the diffusingsection, may be fabricated from steel or other suitable materialcommonly used in the manufacture of sterilizer chambers. Since thechamber will be operating very close to atmospheric pressure, thechamber need not be made to withstand heavy vacuums or high pressures,unless the pressure during the sterilizing cycle is high. The preferredsterilizing gas will be a mixture of 12% ethylene oxide and 88%dichlorodifluoromethane although any standard gas mixtures may be used.For example, any of the following mixtures could be used:

(1) ethylene oxide, 90% carbon dioxide, sometimes referred to ascarboxide;

(2) 20% ethylene oxide, 80% carbon dioxide, known in the trade as Oxfume20;

(3) 12% ethylene oxide, 88% dichlorodifluoromethane, known as Pennoxide;

(4) 11% ethylene oxide, 79% trichlorofiuoromethane, 10%dichlorodifiuoromethane, known as Cryoxcide; and

(5) 11% ethylene oxide, 54% trichlorofiuoromethane, 35%dichlorodifluoromethane, known as Benvicide.

The gas mixture may be preheated in the preheat chamber 18, which willbe connected in series with the inlet pipe 19. The porous member 20supported over the inlet 15 prevents the glass beads 17 from fallinginto and obstructing the inlet passage. The line 19 may be connected toa tank of ethylene oxide or other microbicidal sterilizing gas. Theporous member 20 could be a screen, perforated metal, or a porous wovensheet, such as nylon.

The beads 17 may be made of glass, stainless steel, or suitable plastic,or any other suitable material. It has been discovered that beadsbetween the range of sizes 2 to 10 mm. in diameter are most eflfective.The beads must have a sufiicient density so that they will not beagitated by the flow of gas through them. The beads must be ofsufiicient size to provide the proper voids between them for diffusingthe gas.

The sides 22 of the inlet chamber may be disposed at an angle ofapproximately thirty-five degrees to a center line drawn through theinlet 15 and outlet 16 and, thus, a generally streamlined even path offlow will be provided from the inlet 15 to the intermediate sterilizingchamber 11. Likewise, the sides of the hood 12 may be disposed at anangle of approximately thirty-five degrees to the line drawn through theinlet 15 and outlet 16, thereby providing a gentle decrease in the crosssectional area and a corresponding increase in velocity of gas. It isimportant that the gas flowing through the sterilizer have a gradualdecrease in velocity from the inlet to the sterilizing chamber and agradaul increase in velocity from the sterilizing chamber to the exit,rather than an abrupt change so that turbulence of the gas and, thus, amixing of gas with the air will not result. The several embodiments ofthe invention shown herein show several structures which distribute thegas from the inlet uniformly over the sterilizing section. The airentrained in the voids between the beads must be swept out as the gaspasses through. The gas may be preheated by the preheater 18. Thepreheater may be heated by means of an electrical coil around the pipeto vaporize the liquified gas.

The gas is introduced into the inlet and into the diffusing section atthe bottom of the sterilizer chamber. It passes through the glass beads17, which reduce its velocity and thus prevent mixing of the sterilizinggas and the air in the sterilizer chamber. The low velocity gas isevenly distributed over the cross sectional area of the sterilizingchamber by the shape of the inlet. Since the gas is generally heavierthan the air in the chamber, it

4 will push or displace the air from the chamber and move it through theoutlet at the top of the chamber. The configuration of the chamber andthe size of the outlet are such that the air is displaced freely,preventing mixing of the air and the displacing sterilizing gas.

Experiment has determined that the velocity of the sterilizing gasentering the chamber should be such as to give approximately one chambervolume change in approximately five minutes. A total of 15 minutesshould be sufficient at this flow rate to completely displace the airfrom the sterilizing chamber and provide a sterilizing gas concentrationof approximately 450 milligrams per liter of ethylene oxide atatmospheric pressure; charging to pressures above atmospheric wouldprovide higher concentrations.

After the air has been displaced from the chamber by the gas, moistureis introduced at the desired concentration level and the sterilizingexposure period began at selected temperature. This temperature may bein the range of 130 F.

The chamber 10 will be provided with all of the conventional piping,controls, and gauges required to carry out the sterilizing cycledesired. Examples of chambers of sterilizers that have controls designedto carry out similar cycles, but not using the displacement ideadisclosed herein are found in Pat. No. 3,068,064 and Pat. No. 2,080,179.Obviously many other gas and steam sterilizing cycles familiar to thoseskilled in the art can be used wherein air is to be removed from achamber with the structure disclosed herein. The same idea disclosedherein can be used with a variety of gases and vapors, for example,substantially the same idea of sweeping out one gas with another couldbe carried out in a sterilizer utilizing steam as the active sterilizingmedium.

When a sterilizing gas is used that is lighter than air, outlet 16, inFIG. 1, can be used as the inlet and the supply of gas connected to thisas the inlet. The inlet 15 would then be used as the outlet for air andgas purged from the chamber.

The inlet 19 may be connected to a supply of air 32 and a supply ofsteam 33. The chamber can obviously be provided with a steam jacket ifit is desired to provide additional heat. The steam to the chamber canbe utilized to moisturize the load or for use in sterilizing. The airsupply from line 32 can be used to purge the gas from the chamber aftera sterilizing cycle.

As an example of one application of the device disclosed, air at 30p.s.i.g. may be suitable. Steam at 270 degrees Fahrenheit and 26p.s.i.g. may be used as the steam supply. Ethylene oxide gas at 1p.s.i.g. may be used. Suitable regulators, piping, and valves to controlthe gas used will be obvious to those skilled in the art.

An alternate embodiment of the invention is shown in FIG. 2, wherein thesterilizing section 110, diffusing section 111, and hood, and door 113,are similar to those shown in FIG. 1. The inlet pipe 119 is likewisesimilar. A suitable outlet will be provided.

Instead of the bed of beads in the bottom of the sterilizing chamber, asintered metal plate 117 having uniform pores 120 evenly distributedover it is shown, which acts as a diffuser. The pores may be in theorder of microns, or a metal plate with holes .001 inch in diameterspaced inch apart can be used.

In the embodiment of the invention shown in FIG. 3, the chamber 210 hasa diffusing chamber 211, a hood, and an intermediate sterilizing chamber213, and door 214, as in the other embodiments. The inlet 215 and outletare provided. Instead of the beads shown in the embodiment of FIG. 1, afilter stone 230 such as a material known as microporous porcelain orsilicon carbide is attached over the inlet 215 so that gas comingthrough the inlet pipe 219 is diffused through the porous stone anddistributed evenly throughout the chamber.

The following examples of gases shown may be used with eitherembodiments of the invention.

Ethylene oxide concentration of 500 milligrams per liter of 88-12 gas;650 milligrams per liter of 8020 gas; and 1600 milligrams of ethyleneoxide per liter of the dilutant gas can be achieved in a sterilizer bysimple air displacement as set forth herein. Thus, a prevacuum withsubsequent charging to greater than atmospheric pressure is not requiredto introduce the sterilizing gas in an adequate concentration.

Concentration of ethylene oxide in excess of approximately 500milligrams per liter will prove no sufficient reduction of exposure timewhen sterilizing freely exposed organisms. At greater than 40 C.,packaged organisms will be influenced by greater diffusion rates athigher concentrations.

The sterilizing examples that follow are merely illustrative of cyclesthat may be used. Obviously other cycles familiar to those skilled inthe art may be used with the chamber and general method disclosedwithout departing from the spirit of the invention. Throughout theexamples, the pressures shown are in pounds-per-square inch gauge.

EXAMPLE I In a chamber having a sterilizer section 24 inches long by 24inches wide by 24 inches high loaded with surgical instruments and othermetallic articles:

(1) Admit ethylene oxide gas to chamber at 1 p.s.i. and 160 F. at a flowrate of 1.8 c.f.m. for minutes to sweep the air out of the load andchamber.

(2) Admit steam to chamber at 2.2 p.s.i. and 130 F. for '5 minutes.

(3) Admit ethylene oxide gas at 7 p.s.i. and 160 F. to increase chamberpressure to 7 p.s.i.

(4) Maintain chamber pressure at 7 p.s.i. for suitable exposure period.

(5) Admit air to chamber at 1.8 c.f.m. at room tem perature for minutes.

EXAMPLE II In a chamber having a sterilizer section 24 inches long by 24inches wide by 24 inches high loaded with surgical towels, gowns and/ orsheets:

(1) Admit ethylene oxide gas at bottom of chamber at 1 p.s.i. and 160 F.at a flow rate of 1.8 c.f.m. for 5 minutes to sweep the air out of theload and chamber.

(2) Admit steam to chamber at 2.2 p.s.i. and 130 F. for 5 minutes andhold.

(3) Admit ethylene oxide gas to bottom of chamber at 7 p.s.i. and 160 F.

(4) Maintain chamber pressure at 7 p.s.i. and 130 F. for suitableexposure period.

(5) Admit air to top of chamber at 1.8 c.f.m. at room temperature for 15minutes.

EXAMPLE III In a sterilizer chamber 24 inches long by 24 inches Wide by24 inches high loaded with towels, gowns and/ or sheets:

(1) Open bottom chamber to drain at atmospheric pressure. Admit steam totop of chamber at 270 F. and 27 p.s.i. at a rate of 1.8 c.f.m. withbottom to sweep the air out of the goods and chamber.

(2) Close opening and admit steam at 270 F. and 27 p.s.i. until pressurein chamber reaches 27 p.s.i. and 270 F.

(3) Maintain the steam inside the chamber at 27 p.s.i. and 270 F.

(4) Reduce pressure in chamber to 0 p.s.i. and admit air to top ofchamber at atmospheric pressure for 15 minutes.

EXAMPLE IV In a sterilizer chamber 24 inches long and 24 inches wide by24 inches high, loaded with surgical instruments and other metallicarticles:

(1) Open bottom chamber drain to atmospheric pressure and admit steam at270 F. and 27 p.s.i. at 1.8

c.f.m. for 5 minutes to sweep the air out of the goods and chamber.

(2) Close drain and admit steam at 270 F. at 27 p.s.i. until chamberpressure and temperature reach 27 p.s.i. and 270 F.

(3) Maintain said chamber at 270 F. and 27 p.s.i. for 10 minutes.

(4) Open drain and admit air at atmospheric pressure to top of chamberfor 15 minutes.

Charging the sterilizer by simple air displacement disclosed herein isat least as effective as charging by preevacuation.

It will be understood that the partition of the diffuser section may bemade of a porous member, such as a woven nylon sheet, a porous block, afine screen, sheet of material having many small holes or many othermaterials.

The foregoing specification sets forth the invention in its preferredpractical forms but the structure shown is capable of modificationwithin a range of equivalents Without departing from the invention whichis to be und'erstood is broadly novel as is commensurate with theappended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A sterilizer comprising a chamber having an inlet and an outlet atopposite ends thereof,

said chamber having an intermediate section,

a hood section joined to said intermediate section, said outlet beinglocated in the end of said chamber containing said hood section,

said hood section gradually reduces in cross section from saidintermediate section toward said outlet,

an exhaust line in fluid communication with said outlet,

a diffuser section, said inlet being located in the end of said chambercontaining said dilfuser section,

said difluser section being attached to said intermediate section andhaving decreased cross section progressively toward said inlet,

difluser means in said diffuser section and in fluid communication withsaid inlet, said difluser means having a plurality of open pathsconnecting said diffuser section to said intermediate section whereby agas admitted through said inlet to said difluser section will flow tosaid intermediate section and said gas will be distributed generallyuniformly over the entire cross sectional area of said intermediatesection substantially without turbulence.

2. The sterilizer recited in claim 1 wherein said diffuser meanscomprises a screen having small holes therein forming a partitionbetween said diffuser section and said intermediate section whereby gasfrom the said inlet may be distributed uniformly over the entire crosssectional area of said intermediate section and gas in said intermedatesection may be moved as a body from the said difluser section to saidhood and thence to said outlet.

3. The sterilizer recited in claim 1 wherein:

said diffuser means comprises a perforated plate having relatively smallopenings therein,

said plate forming a partition between said dilfuser section and saidintermediate section,

said holes being generally uniformly distributed over said plate wherebygas from said inlet is directed to said difluser section and from saiddiffuser section through said openings in said plate to saidintermediate section whereby gas in said intermediate section is movedtoward said outlet generally as a body.

4. The sterilizer recited in claim 1 wherein said diffuser meanscomprises a porous stone disposed over said inlet and adapted to diffusegas from said inlet generally uniformly through said diffuser sectionand thence to said 8 intermediate section whereby gas in saidintermediate sec- 8. The sterilizer recited in claim 7 wherein an airtion is moved toward the outlet generally without tursupply and a steamsupply are connected to said inlet. bulence. 9. The sterilizer recitedin claim 7 wherein an air 5. The sterilizer recited in claim 1 whereinsaid difsupply and a sterilizing gas are connected to said inlet. fusersection is generally in the shape of a truncated 5 cone. ReferencesCited 6. The sterilizer recited in claim 1 wherein said hood UNITEDSTATES PATENTS section is generally in the form of a truncated cone.

7. The sterilizer recited in claim 1 wherein said diffuser meanscomprises: 10

a plurality of pellets disposed in said diffuser section g gi defining abed extending substantially to said inter- 2451073 10/1948 Cowheramediate section,

the area of said bed of pellets adjacent said difiuser gig section atthe section where it is attached to said 15 intermediate section beingsubstantially equal to the MORRIS WOLK, Primary Examiner cross sectlonalarea of sa1d intermediate section whereby gas entering said inlet isdiffused uniformly L RICHMAN, Asslstant EXamlIlel' throughout saidintermediate section and said gas flows uniformly through saidintermediate section to 20 said outlet. 2156, 58, 92, 93, 94, 95, 109;23290

